The invention relates to lifting fixtures used to precisely control the attitude of loads being handled by overhead cranes.
In many aerospace and related industries, the loads being lifted by cranes are expensive, delicate, and require precise manipulation at many stages in the manufacturing process. This problem has been solved in the past by the design and construction of a large array of special fixtures or adapters each of which permit a single type load to be lifted. It is desirable from a cost and schedule standpoint to have a more universal solution. Specifically, it is desirable to have a single device that adapts itself to a larger number of load types.
In lifting any load with an overhead crane, stability requires that the center of gravity of the load has to be directly below the hook. An automatic system must move the load in two dimensions relative to the hook so that a stable lift is possible. However, an automated system, especially one that is lifting heavy items, could easily injure personnel and damage equipment if a malfunction occurred. Of particular concern would be a “runaway” drive element, which would swing the load. Moreover, an ease of use is important to efficient manufacturing operations and computerized control is the current state of the art way to achieve such ease of use.
The present invention increases the reliability of a self-adjusting load bar by means of a safety architecture that facilitates preventing a “runaway” malfunction without compromising the ease of use.